Reactivation Performance of Nitrosation Flocculent Sludge After Long-term Storage

Abstract

In order to explore the nitrogen removal performance of nitrosation flocculent sludge subject to long-term storage, nitrosation flocculent sludge which had been stored at 4℃ for ten months was inoculated in a continuous stirred tank reactor (CSTR) to investigate its activity recovery performance. MiSeq high throughput sequencing technology was also employed to analyze the structure of the microbial community before and after reactivation. Results showed that, under DO control of DO 0.4-0.8 mg·L-1, pH value of about 8 and temperature of (30±1)℃, the sludge could be reactivated in 15 days. Both the removal efficiency of ammonia nitrogen and the accumulation ratio of nitrite nitrogen were higher than 90%. The color of the sludge quickly changed from grey at early inoculation to brown, while the sludge volume index (SVI) quickly decreased and both mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) and extracellular polymer substances (EPS) significantly increased. With the recovery of nitrosation performance, anaerobic and heterotrophic bacteria were washed out, the relative abundance of ammomia-oxidizing bacteria such as Nitrosomonas significantly increased, while the growth of nitrite-oxidizing bacteria such as Nitrospria was selectively inhibited. Nitrosation flocculent sludge could be inoculated after long-term storage to achieve rapid start-up of partial nitrification and allow practical application of partial nitrification processes.